INFLUENCE OF ENVIRONMENT 347 



the foster mother as Guthrie supposed — a 

 thing which has been disproved by Castle 

 (Figs. 81 and 82)? Why do dominant and 

 recessive characters remain pure, even after 

 their intimate union in a hybrid, so that pure 

 dominants and pure recessives may be obtained 

 in subsequent generations from this mixture? 

 Why does every child have to learn anew what 

 his parents learned so laboriously before him? 

 Even the strongest defenders of the inheri- 

 tance of acquired characters are constrained 

 to admit that it occurs only sporadically and 

 exceptionally. 



Many modifications of the Lamarckian hy- 

 pothesis of the inheritance of acquired char- 

 acters have been proposed in recent years. 

 Foremost among these are the "mneme" 

 theory of Semon and the "centro-epigenesis" 

 theory of Rignano. To Semon as to many 

 other biologists the apparent resemblance be- 

 tween memory and heredity has seemed sig- 



All the offspring are pure black, though both parents are 

 pure white, because the white female contains only "black" 

 eggs and black is dominant over white. (From Castle.) 



